package org.apache.commons.graph.algorithms.visit

import org.apache.commons.graph.Graph

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

/**
 * Base NOOP [GraphVisitHandler] implementation.
 *
 * @param <V> the Graph vertices type
 * @param <E> the Graph edges type
</E></V> */
open class BaseGraphVisitHandler<V, E, G : Graph<V, E>, O> : GraphVisitHandler<V, E, G, O> {
    /**
     * {@inheritDoc}
     */
    override fun discoverEdge(head: V, edge: E, tail: V): VisitState {
        // do nothing
        return VisitState.CONTINUE
    }

    /**
     * {@inheritDoc}
     */
    override fun discoverGraph(graph: G) {
        // do nothing
    }

    /**
     * {@inheritDoc}
     */
    override fun discoverVertex(vertex: V): VisitState {
        // do nothing
        return VisitState.CONTINUE
    }

    /**
     * {@inheritDoc}
     */
    override fun finishEdge(head: V, edge: E, tail: V): VisitState {
        // do nothing
        return VisitState.CONTINUE
    }

    /**
     * {@inheritDoc}
     */
    override fun finishGraph(graph: G) {
        // do nothing
    }

    /**
     * {@inheritDoc}
     */
    override fun finishVertex(vertex: V): VisitState {
        // do nothing
        return VisitState.CONTINUE
    }

    /**
     * {@inheritDoc}
     */
    override fun onCompleted(): O? {
        return null
    }
}
